Catheter with improved torque transmission

ABSTRACT

A catheter has a deflection beam and a single continuous puller wire to effectuate bi-directional deflection. A joint between a catheter body and a deflectable distal section effectively transmits torque from a control handle. The joint includes two open-shaped brackets, each affixed to a respective side of the flat deflection beam to form a closed-shaped hollow body that bridges and circumferentially encircles the beam. Each bracket has through-holes into which thermoplastic material of the catheter body and the deflectable distal section can melt and migrate to form interlocking nodes.

FIELD OF INVENTION

The present invention relates to a medical device for use in the vesselof a patient for the purpose of diagnosing or treating the patient, suchas mapping tissue and/or ablating tissue using radio frequency (RF) orother sources of energy. More particularly, the invention relates to alonger deflectable catheter having a flat beam for on-planebi-directional deflection with improved torque transmission, and methodof making same.

BACKGROUND

Electrode catheters have been in common use in medical practice for manyyears. They are used to stimulate and map electrical activity in theheart and to ablate sites of aberrant electrical activity. Atrialfibrillation is a common sustained cardiac arrhythmia and a major causeof stroke. This condition is perpetuated by reentrant waveletspropagating in an abnormal atrial-tissue substrate. Various approacheshave been developed to interrupt wavelets, including surgical orcatheter-mediated atriotomy. Prior to treating the condition, one has tofirst determine the location of the wavelets. Various techniques havebeen proposed for making such a determination, including the use ofcatheters with a mapping assembly that is adapted to measure activitywithin a pulmonary vein, coronary sinus or other tubular structure aboutthe inner circumference of the structure. One such mapping assembly hasa tubular structure comprising a generally circular main regiongenerally transverse and distal to the catheter body and having an outercircumference and a generally straight distal region distal to the mainregion. The tubular structure comprises a non-conductive cover over atleast the main region of the mapping assembly. A support member havingshape-memory is disposed within at least the main region of the mappingassembly. A plurality of electrode pairs, each comprising two ringelectrodes, are carried by the generally circular main region of themapping assembly.

In use, the electrode catheter is inserted into a guiding sheath whichhas been positioned a major vein or artery, e.g., femoral artery, andguided into a chamber of the heart. Within the chamber, the catheter isextended past a distal end of the guiding sheath to expose the mappingassembly. The catheter is maneuvered through movements that includedeflection of a distal portion of the catheter so that the mappingassembly is positioned at the tubular region in the heart chamber. Theability to control the exact position and orientation of the catheterand also the configuration of the mapping assembly is critical andlargely determines how useful the catheter is.

Steerable catheters are generally well-known. For example, U.S. Pat. No.Re 34,502 describes a catheter having a control handle comprising ahousing having a piston chamber at its distal end. A piston is mountedin the piston chamber and is afforded lengthwise movement. The proximalend of the elongated catheter body is attached to the piston. A pullerwire is attached to the housing and extends through the piston, throughthe catheter body, and into a tip section at the distal end of thecatheter body. The distal end of the puller wire is anchored in the tipsection of the catheter. In this arrangement, lengthwise movement of thepiston relative to the housing results in deflection of the catheter tipsection.

The design described in U.S. Pat. No. RE 34,502 is generally limited toa catheter having a single puller wire. If bi-directional deflection isdesire, more than one puller wire becomes necessary. Catheters adaptedfor on-plane bi-directional deflection are also known. A flat beam isnormally provided to enable deflection on both sides of the beam withina plane. However, the puller wire in tension under deflection oftenflips over to the other side of the beam, or where the puller wires arelocated close to the beam, a large bending moment is required to deflectthe beam, imposing significant stress on the puller wires. Moreover,with the puller wires close and tightly constrained to the beam,adhesion failure or rupture of the constraint poses a risk.

The employment of a pair of puller wires to effectuate bi-directionaldeflection also required a number of components which occupied space ina space-constrained catheter. More components also increased the risk ofcomponent failures. The use of T-bars and/or crimps can unduly fatiguepuller wires and impart shear stresses resulting from skewed or off axisalignment of puller wires relative to the longitudinal axis of thecatheter, even if by a minor degree. While bi-directional deflection isunquestionably an improvement over uni-directional deflection,bi-directional deflection is typically symmetrical whereas many regionsof the heart lack symmetry. Thus, it would be desirable to provide acatheter with more deflection variety and options.

With catheters that have long deflectable tip designs (e.g., 90-180 mmor longer) that utilize a flat deflection beam as part of the tipsteering mechanism, there is a need to provide a transition between thecatheter shaft and the deflectable tip that transfers torsional forcesfrom the control handle to the tip with high fidelity and lowhysteresis, to provide the physician or user the ability to accuratelyplace and control the tip deflection within the patient.

Accordingly, a need exists for a catheter with long deflectable tipdesigns using a deflectable beam capable of predictable on-planebi-directional deflection (symmetrical and nonsymmetrical) which employsa flat deflection beam which can be deflected easily without significanttensile or shear stress on the puller wires and provides a transitionbetween the catheter body and deflectable tip that can transmit torquefrom the control handle to the deflectable tip.

SUMMARY OF THE INVENTION

The present invention is directed to a catheter having a deflection beamand a single continuous puller wire to effectuate bi-directionaldeflection with less deflection components for reducing catheter sizewithout compromising functionality, including the ability to carry,house and support mapping and/or ablation components, such as amultitude of electrodes and lead wires. In one embodiment, the catheterhas a catheter body and a distal section with a flat deflection beam,and a single continuous puller wire that extends from a control handle,up along the catheter body and one side of the beam, and U-bends arounda distal end of the flat beam. The puller wire then runs back down alongthe other side of the flat beam, down the catheter body and back intothe control handle. The catheter advantageously provides a joint betweenthe catheter body and the distal section that is particularly effectivein transmitting torque from the control handle to the catheter body andthe distal section. Each of the catheter body and the distal section hasa tubular structure with a central lumen. Each tubular structure has atleast an inner layer of a thermoplastic material. The joint includes twoopen-shaped brackets, each of which is affixed to a respective side ofthe flat deflection beam so as to face other and form a closed-shapedhollow body that bridges and circumferentially encircles the beam at thejoint while allowing components to pass through the joint uninterrupted.A distal end of the catheter body is slipped on a proximal end of thehollow body and a proximal end of the deflectable section is slipped ona distal end of the hollow body. Each bracket has recesses orthrough-holes into which the thermoplastic material of each tubularstructure can melt and migrate to form interlocking nodes with theapplication of heat and pressure, for example, by utilizing a two piecethermal fusing die. A heat shrink tubing may be placed over the jointduring heat fusion and removed after cooling.

In a more detailed embodiment, each bracket has a half cylindrical shapewith a “C” cross-section along its length and two longitudinal sideedges. Affixed to opposite of the flat beam along the side edges, a pairof bracket forms a hollow cylindrical body around the beam at the joint.The brackets are constructed of any suitable materials, including fullhard, cold worked stainless steel alloys (304 or 316 full hardcondition), nickel/titanium alloys (nitinol) or phosphor bronze alloysThey may be coated with adhesive for better bonding with thethermoplastic material of the tubular structures.

In another more detailed embodiment, each tubular structure also has alayer of braided mesh over the thermoplastic material, and an outerlayer of an elastomeric material.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features and advantages of the present invention will bebetter understood by reference to the following detailed descriptionwhen considered in conjunction with the accompanying drawings. It isunderstood that selected structures and features have not been shown incertain drawings so as to provide better viewing of the remainingstructures and features.

FIG. 1 is a top plan view of a catheter in accordance with oneembodiment of the present invention.

FIG. 2 is a side cross-sectional view of a transition section between acatheter body and a deflectable section of the catheter of FIG. 1 inaccordance with one embodiment of the present invention.

FIG. 2A is an end cross-sectional view of the transition section of FIG.2, taken along line A-A.

FIG. 3A is a perspective view of an interior of a deflectable section,including one side of a deflection beam.

FIG. 3B is a perspective view of the interior of the deflectable sectionof FIG. 3A, including the other side of the deflection beam.

FIG. 4 is a side cross-sectional view of a portion of a deflectablesection, including a distal end of a deflection beam, in accordance withan embodiment of the present invention.

FIG. 4A is an end cross-sectional view of the deflectable section ofFIG. 4, taken along line A-A.

FIG. 4B is an end cross-sectional view of the deflectable section ofFIG. 4, taken along line B-B.

FIG. 4C is an end cross-sectional view of the deflectable section ofFIG. 4, taken along line C-C.

FIG. 4D is an end cross-sectional view of the deflectable section ofFIG. 4, taken along line D-D.

FIG. 5A is a top plan view of a distal end of a deflection beam, inaccordance with one embodiment of the present invention.

FIG. 5B is a bottom plan view of the distal end of the deflection beamof FIG. 5A.

FIG. 5C is a top plan view of the distal end of the deflection of FIG.5A, with a portion removed, as assembled with a support member of adistal assembly, in accordance with one embodiment of the presentinvention.

FIG. 6A is an end cross-sectional view of a deflection beam with aspacer on each side, in accordance with one embodiment of the presentinvention.

FIG. 6B is an end cross-sectional view of a deflection beam with aspacer on each side, in accordance with another embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to a catheter having a catheter shaftand a deflectable distal portion having an elongated flat beam or“blade” to effectuate bi-directional deflection while maximizing spacewithin the catheter for components including lead wires, puller wires,cables, tubings and any other support members for advanced distal dipdesigns. With reference to FIG. 1, a catheter 10 in accordance with anembodiment of the present invention includes a catheter shaft 12, adeflectable distal section 14 distal of the catheter shaft, and acontrol handle 16 proximal of the catheter shaft. The deflectablesection 14 has a tip assembly 15 having, for example, a lasso designwith a generally circular main portion extending and orientedtransversely from a distal end of the deflectable section 14.Advantageously, the deflectable section 14 supporting the tip assembly15 is configured for nonsymmetrical bi-directional deflection with onecurvature or deflection DA on one side of the catheter and anothercurvature or deflection DB on the other side. Deflection is effectuatedby user manipulation of an actuator 13 provided on the control handle 16which moves a puller wire that extends along the catheter from thecontrol handle 16, through the catheter body and into the distal section14.

With reference to FIGS. 2 and 2A, the catheter body 12 is an elongatedtubular structure comprising a single, central or axial lumen 18. Thecatheter body 12 is flexible, i.e., bendable, but substantiallynon-compressible along its length. The catheter body 12 may be of anysuitable construction and made of any suitable materials. In oneembodiment, the catheter body 12 is multi-layered comprising at least aninner coat or layer 20, and an outer coat or layer 22 with an imbeddedbraided mesh 21 of stainless steel or the like to increase torsionalstiffness of the catheter body 12 so that, when the control handle 16 isrotated, the deflectable portion of the catheter 10 rotates in acorresponding manner. The outer diameter of the catheter body 12 is notcritical, but is preferably no more than about 8 French. Likewise thethicknesses of the layers 20 and 22 are not critical.

The deflectable section 14 is a shorter tubular structure having asimilar construction to the tubular structure of the catheter body 12except with greater flexibility. In the embodiment of FIGS. 2 and 2A,the deflectable section 14 has a central lumen 19 and a multi-layeredconstruction comprising at least an inner coat or layer 24, and an outercoat or layer 26 with an imbedded braided mesh 25 of stainless steel orthe like. The outer diameter of the deflectable section 14 is similar tothe catheter body 12, at preferably no more than about 8 French.Suitable materials for the inner layers 20 and outer layer 24 includematerials with high heat deflection temperatures so deflectioncharacteristics are not modified by the patient's body temperature.

Suitable materials for the layers of the catheter body 12 and thedeflectable section 14 include materials with moderate heat deflectiontemperatures so stiffness of the deflection section 14 and thus itsdeflection characteristics are not modified by introduction into thepatient's body due to temperature variations. Suitable materials for theinner and outer layers 20 and 22 of the catheter body 12 include Pebaxand Pellethane. Materials particularly suitable for both the inner andouter layers 20 and 22 include lower shore hardness plastics rangingfrom 25-55 D.

Suitable materials for the inner and outer layers 24 and 26 ofdeflectable section 14 include polyurethane or PEBAX. In one embodiment,the tubular structure 17 of the deflectable section 14 includes anextruded braided structure, with the inner layer 24 having a thicknessranging between about 0.002 inch to 0.003 inch of natural “sticky”2533-SA-01 PEBAX, then braided with 0.0016 inch diameter, PEN braid(50-80 pics per inch), and the outer layer 26 including extruded PEBAX5533-SA-01 or 4033-SA-01 PEBAX with about 25% barium sulfate added forradiopacity.

Extending through the length of the deflectable section 14 is anelongated support structure configured as a flat beam or “blade” 30(“beam” and “blade” used interchangeably herein) with a rectangularcross-section R having a greater width W and a lesser thickness T, asshown in FIG. 2A, defining two opposing rectangular face surfaces FA andFB (or sides, used interchangeably herein) FA and FB that are flat orsmooth, and two opposing edge surfaces E1 and E2 that arefriction-inducing, e.g., uneven, rough, textured or serrated to provideraised and/or recessed formations along longitudinal edges of the beam30. The beam 30 may be constructed of any suitable high yield strengthmaterial that can be straightened or bent out of its original shape uponexertion of a force and is capable of substantially returning to itsoriginal shape upon removal of the force. Suitable materials for thesupport beam 30 include full hard, cold worked stainless steel alloys(304 or 316 full hard condition), nickel/titanium alloys (nitinol) orphosphor bronze alloys. Nitinol alloys typically comprise about 55%nickel and 45% titanium, but may comprise from about 54% to about 57%nickel with the balance being titanium. A suitable nickel/titanium alloyis nitinol, which has excellent shape memory, together with ductility,strength, corrosion resistance and temperature stability. The beam 30effectively divides or bisects the central lumen 19 of the deflectablesection 14 into two half-spaces 19A and 19B. Components such as leadwires, cables, and tubings can pass through either space withoutsignificant interruption or obstruction.

In accordance with a feature of the present invention, the catheter 10has exceptional torque transmission capability provided by a joint ortransition section 65 between the catheter shaft 12 and the deflectablesection 14, as shown in FIGS. 3A and 3B. The transition section 65transfers torsional forces from the control handle 16 to the distalassembly 15 with high fidelity and low hysteresis, to provide a userwith a means to accurately place and control the distal assembly 15within the patient. The transition section 65 includes a pair ofopposing elongated brackets 66A, 66B, each with an “open” configurationthat when affixed to opposite surfaces of the beam to face each othertogether forms hollow body with a “closed” configuration thatcircumferentially surrounds the beam at the joint. The brackets and thebody formed thereby bridge the abutting ends of the tubular structuresof the catheter body 12 and the deflectable section 14. The brackets,which can be formed by die cutting or acid etching, provide receivingformations, including recesses, or through holes (e.g., circularperforations or punched through-holes 68) arranged in a predeterminedpattern. In one embodiment, the pattern includes a plurality oftransverse rows, with adjacent rows being offset although it isunderstood that other alternating or offset patterns would be suitable,as well. In the illustrated embodiment, there are eleven through-holes,with transverse rows R1, R3, R5 and R7, each with two through-holes, androws R2, R4 and R6 having one through-hole, with adjacent rows offset bya distance equal to about a diameter or width of a perforation. Thebrackets 66A, 66B can be constructed of the same material as the blade30 and may be pre-coated with an adhesive for higher bond strengthduring heat fusion, as described further below.

In the illustrated embodiment, each bracket has a half cylindrical bodywith a uniform semi-circular or “C” shape cross section along its lengthand is affixed to a respective side of the blade 30 along its two outerside edges 69, e.g., by resistance spot welding, brazing or laserwelding, to face each other and jointly form a full cylindrical body 66(used interchangeably with the brackets 66A, 66B) generally surroundingthe blade 30 at the transition section. The body 66 overlaps theabutting ends of the catheter body 12 and the deflectable section 14. Adistal end of the tubular structure 11 of the catheter body 12 ismounted on or slipped over a proximal end of the body 66, and a proximalend of the tubular structure 17 of the deflectable body 14 is mounted onor slipped over a distal end of the body. In that regard, the blade 30on which the body 66 is affixed has a proximal end that extends a shortdistance into the distal end of the catheter body 12. As best shown inFIG. 2A, the body 66 defines a central lumen 67 that is divided orbisected by the blade 30 into two cavities 67A and 67B through whichcomponents, such as lead wires, cables, etc., can pass. The length ofthe body 66 ranges between about 5 mm and 12 mm, preferably betweenabout 6.5 mm and 10 mm.

With reference to FIG. 2, in assembling the transition section 65,distal end 12D of the catheter shaft 12 is slid onto the proximal end ofthe cylindrical body 66 with proximal end 30P of the blade 30 extendinga short distance into the central lumen 18. A proximal end 14P of thedeflectable section 14 is slid onto the distal end of the cylindricalbody 66 with the blade (and its deflection components) extending throughthe central lumen 19 toward the distal end of the section 14.Accordingly, the distal end 14D of the deflectable section 14 and theproximal end 12P of the catheter shaft 12 extend over the body 66 fromopposite directions such that they abut each other at or near amid-location along the length of the body 66. The inner coatings 20 and24, if not also the outer coatings 22 and 26, are then fused to the body66, with application of sufficient heat and pressure so as to melt,migrate and/or flow to form interlocking nodes 20N and 24N into theperforations 68. This fusion creates a very strong interlocking bondbetween the catheter shaft 12 and the deflectable section 14. The nodesincrease the axial load capacity to the joint. In fact, the resultingtorque transmission bond joint can be stronger in torsion and in tensileforce loading than the braided catheter shaft 12 and deflectable section14 that are bonded to it.

To facilitate the application of heat and pressure to the transitionsection 65, a protective heat-shrink tubing 70, e.g., fluorinatedethylene propylene (FEP) or polyethylene terephthalate (PET) is placedover the transition section to form a tube assembly, and shrunken(“recovered”) over the transition section (e.g., by a heat gun or oven)to apply inward pressure against the body 66. The tube assembly is thenplaced in a two-piece heat fusing die head (not shown) for heating tomelt (“reflow”) the inner layers 20 and 24 of the tubular structures 11and 17 of the catheter body 12 and deflectable section 14 to form theinterlocking nodes 20N and 24N. The tube assembly is then cooled. Theheat shrink tubing 70 can be used as a process aid to prevent the meltedlayers from contacting the heated die and create a uniform transitionbetween the mating tubular bodies of the catheter body 12 anddeflectable section 14. Thus, the shrink tubing 70 is removed from thetransition section 65 after the fusing process.

The heat fusing die head utilizes a highly accurate fusing die heightmeasurement indicator (LVDT) to sense fusing die head movement duringthe heating/fusing process. Since the construction materials of thecoatings of the shaft 12 and the deflectable section 14 may includeextruded raw thermoplastic polymers with a wide range of heat histories(±25° F.) between material lots, monitoring the softening of thepolymers and the resultant die head movement is another means besidestemperature measurement to achieve process control while reducing theinfluence of polymer heat history during the heating/fusing process.Moreover, the transition section can be created in minimal duration(e.g., less than about 60 seconds) using a thermal fusing machine thatis water-cooled to provide fast cycle times. The transition section isadvantageously homogenous and seamless. The structure of the transitionsection is nondiversified once heat-pressure fuse operation iscompleted.

In accordance with a feature of the present invention, the catheter 10provides bi-directional deflection with a single continuous puller wire28 that advantageously requires less actuation force by a user andimposes less shear stress on the puller wire. Similar to conventionalbi-directional catheters that use a pair of puller wires whose proximalends are anchored in the control handle, proximal ends of the singlecontinuous puller wire 28 are anchored in the control handle 16.However, the puller wire 28 bends upon itself to form a portion 28M witha U-bend (about 180 degrees) at or near a midpoint along its length,with the U-bend being the distal-most portion of the puller wire in thecatheter. As shown in FIG. 4, the U-bend mid-portion 28M divides thepuller wire into two main proximal segments 28A and 28B of generallyequal length, each with a proximal end that is anchored in the controlhandle 16. With reference to FIGS. 5A, 5B and 5C, to anchor the U-bendportion 28M at a distal location on the catheter, a distal end of theblade 30 has a receiving formation 32 e.g., either an on-axis slit 32Sor an on-axis through hole 32H which securely receives the mid-portion28M so that each long portion 28A and 28B extends centrally alongside arespective face surface FA, FB of the blade 30. This arrangementadvantageously avoids the use of conventional T-bars, crimp typeconnections, soldering or welding as a means to attach the puller wireto the blade 30. Because the puller wire is not rigidly attached to theblade 30, this arrangement provides smooth bi-directional steering.

As illustrated in FIGS. 5A and 5B, the distal end of the blade 30 has anoriginal configuration prior to assembly of the catheter and attachmentof the puller wire 28 which includes an elongated longitudinal closedslit 32S with a distal end 31 and a proximal end 33. The slit 32S isdisposed immediately proximal of a distal end portion 30D of the blade30. The through-hole 32H is disposed in the distal end portion 30D. TheU-bend mid portion 28M of the puller wire may be inserted and hookedthrough the hole 32H, or alternatively in the slit 32S at its proximalend 33. In the latter regard, the slit 32S is adapted into an openconfiguration from a closed configuration for receiving the U-bendmid-portion 28M when the distal end portion 30D of the blade is detachedby a user bending or cutting along a transverse “pre-cut” groove 52(FIG. 5A) provided on the face FA of the blade 30 proximal of the hole32H. In the illustrated embodiment, a first transverse groove 52 a isaligned with the distal end 31 of the slot 32 and a second (half width)transverse groove 52 b is aligned at or near a midpoint along the lengthof the slot 32S. Thus, the distal end portion 30D can be readily brokenoff or otherwise detached from the blade along the groove 52 a. Foreasier access to open slit 32S, another portion 30A can be detached fromthe blade 30 along the groove 52 b, as shown in FIG. 5C.

As shown in FIG. 5C, the slit 32S is generally centered and on-axis withthe longitudinal axis of the blade 30 such that the slit divides theblade alongside into two generally equal elongated sections or halves 54a, 54 b. On selected section 54 a, a hollow tube or ferrule 60 (e.g., ofstainless steel) is laser welded to face FA of the section 54 a. Aproximal end of a support member 72 supporting the distal assembly 15 isinserted and anchored in the tube 60, e.g., by crimping, to create aninterference fit between the tube and the support member to transmittorque and tension/compression forces from the blade to the distalassembly. A mechanical crimp process eliminates problematic adhesivebonding that can loosen or fail causing the distal assembly 15 to spin.A servo process with precision force control is sued to detect a definedforce slope so that acceptable interference between the support member72 and the tube 60 is created without damaging the puller wire 28.

Where the deflection blade 30 has equal stiffness on both faces alongits longitudinal axis, deflection on either side of the blade has asimilar deflection initiation location (or curve generation location)and the catheter provides symmetrical bi-directional deflection.However, in accordance with a feature of the present invention, theblade 30 has a different deflection initiation location on each side,thereby providing nonsymmetrical bi-directional deflection. Withreference to FIG. 1, the blade 30 has different and “independent”deflection on each side such that deflection on one side does notinfluence or affect deflection on the other side. In the embodiment ofFIG. 1, side FA of the blade 30 has deflection initiation location A ata distal location, as provided by a lumened stiffener 50A, e.g., apre-loaded compression coil, affixed to one side of the blade. Thecompression coil 50A is flexible in elongation but resists compressionand thus it provides a deflection initiation location A at or near itsdistal end. The compression coil has a proximal end generallycoterminous with the proximal end of the catheter shaft 12. It extendsthrough the central lumen 18 of the catheter shaft 12. In thedeflectable section 14, the compression coil 50A lies on the side FA ofthe blade 30 along a center longitudinal axis of the blade, as shown inFIGS. 3A and 4. Throughout the catheter shaft 12 and the deflectablesection 14, the puller wire segment 28A extends through a central lumenof the compression coil 50A (FIG. 2A). Accordingly, when the blade 30 isdeflected toward the side FA, the coil 50A is in compression and behavesas a rigid column, especially when further constrained by a heat shrinktube cover 53, e.g., of thin-walled PET. Thus, deflection on the side FAbegins and occurs distal of the compression coil 50A with a deflectioninitiation location A at or near the distal end of the compression coil.

In contrast, when the blade 30 is deflected toward the side FB oppositeof the compression coil 50A, the compression coil is in tension anddeflects along with the blade 30 toward side FB along the length of theblade 30. In that regard, a second compression coil is provided for thepuller wire segment 50B (FIG. 2). Throughout the catheter shaft 12, thepuller wire segment 28B extends through a central lumen of thecompression coil 50B. The compression coil 50B has proximal and distalends that are generally coterminous, respectively, with the proximal anddistal ends of the catheter shaft 12. In the illustrated embodiment, thedistal end is a short distance proximal of the proximal end of the beam30. Thus, deflection on the side FB begins and occurs distal of thecompression coil 50B with a deflection initiation location B at or nearthe distal end of the catheter shaft 12.

With this configuration, each side of the blade has a differentdeflectable working length and two distinct curvatures can be created inthe deflectable section 14 using a single continuous puller wire. Asillustrated, the side FA of the blade 30 with the compression coil 50has a tighter or sharper curvature with a smaller defined radius and amore distal deflection initiation location A compared to the oppositeside FB of the blade 30 which has a looser, larger and gentler curvaturewith a greater defined radius and a more proximal deflection initiationlocation B. Accordingly, the deflectable working length of side FA isshorter than the deflectable working length of side FB.

As shown in FIGS. 3A and 4, a stop, e.g., in the form of a stop tube 62,is provided to affix the distal end of the compression coil 50 to theblade 30. The stop tube 62 has an outer diameter which is generallyuniform along the length of the stop tube, and an inner bore 63 toreceive at its proximal end the distal end of the compression coil 50with a slip fit. The inner bore 63 has a larger inner proximal diameterto accommodate the compression coil 50 and a smaller inner distaldiameter through which the puller wire 28A passes.

In one embodiment, the larger proximal inner diameter is between about0.001-0.003 inches larger than the compression coil diameter. Thesmaller distal inner diameter is between about 0.003-0.006 inchessmaller than the compression coil diameter. Where the stop tube 62 has alength L, the length or longitudinal span of the larger proximal innerdiameter bore ranges between about 0.6 L to 0.8 L and the length orlongitudinal span of the smaller distal inner diameter ranges betweenabout 0.2 to 0.4 L.

The stop tube 62 may be affixed to the blade 30, e.g., by resistancewelding, in a location slot or recess 64 formed on the face FA for easyplacement and alignment. The recess 64 may be acid etched.

Proximal ends of the portions 28A and 28B are anchored in the controlhandle 16 and deflection mechanism in the control handle 16 responsiveto the actuator 13 manipulated by a user is configured to draw on aselected proximal end of the puller wire along one side of the blade 30to deflect the catheter with a distinct curvature on that one side. Thepuller wire 28 may be coated with PTFE or Teflon so the long portions28A and 28B can slide smoothly inside the protective tubes 36A, 36B whenthe portions are drawn distally by the deflection mechanism.

As understood by one of ordinary skill in the art, the puller wire 28 isin tension to create a bending moment to deflect the blade 30 in thedesired direction. Conventional catheter with a flat blade may use apuller wire with a rectangular cross-section that is welded and tightlyconstrained to the blade to prevent adhesion failure. While this designmay be simple and compact in certain respects, the puller wire is undersignificant force due because of its close proximity to the blade, whichin pure bending requires a substantial bending moment stress duringdeflection. In contrast, the catheter of the present invention isconfigured to provide a spacer 90 of a predetermined thickness toseparate the puller wire 28 and a neutral bending axis NA of the blade30 by a predetermined distance so as to lower the force on the pullerwire, including the bending moment. Moreover, the catheter 10 includes apuller wire with a round (or at least nonrectangular) cross section toreduce the area moment of inertia, as an otherwise rectangular pullerwire with the same cross-sectional area separated from the neutral axisby a comparable spacer would unduly increase the size/diameter of thecatheter and the area moment of inertia to result in an unacceptablystiff catheter.

In one embodiment as shown in FIG. 6A, the spacer 90A and 90B on eachside of the blade 30 includes a first inner adhesive layer 34A, 34B anda wall of a lumened elastomeric puller wire tube 36A, 36B. The adhesivelayer may be an ultra high temperature adhesive transfer tape 34A and34B sold by 3M under the model 100HT. The tube 36A, 36B, which may beconstructed of polyimide, is affixed to the respective adhesive layer34A, 34B and a respective puller wire proximal portion 28A and 28Bextends through its lumen 37. An interior surface of the tubing 36surrounding the puller wire may be coated with PTFE e.g. TEFLON toreduce friction with the puller wire. On side FA, the spacer 90A runslongitudinally from near the receiving formation 32 and the U-bendportion 28M to near a distal end of the stop tube 62. On side FB of theblade 30, the spacer 90B runs generally the entire length of the blade30. Thus, in the deflectable section 14 and along the blade 30, thepuller wire is without the spacer 90 in the U-bend portion 28M andthrough the compression coil 50. Alternatively, the spacer 90 mayinclude extrusions 92A and 92B surrounding the puller wire as shown inFIG. 6B. The extrusions 92, which may be made of PEEK, has across-sectional shape that has a main round or circular portion (tomatch and surround the round puller wire) and a thin wide elongated baseportion with rounded corners that interfaces with the surfaces FA andFB. The rounded corners advantageously reduce material stressconcentrations during deflection.

The round puller wire 28 has a diameter D ranging between about 0.007inch and 0.009 inch, and preferably about 0.008 inch. The blade 30 has athickness T of about 0.004 inch and 0.007 inch, and preferably betweenabout 0.005 inch and 0.006 inch. The puller wire and the neutral axisare separated by a distance d, ranging between about 0.008 inch and0.025 inch, and preferably between about 0.10 inch and 0.015 inch.

In the embodiment of FIGS. 6A and 6B, the diameter D is 0.008 inch, theblade thickness is 0.005 inch and the distance d is 0.0105 inch, leavinga separation d between the puller wire and the adjacent surface of theblade (and a spacer thickness) of 0.004 inch. Compared to a rectangularpuller wire with the same cross sectional area (e.g., 0.010 inch×0.005inch), the puller wire force can be reduced by at least half to createthe same bending moment to deflect the blade. The stress force on thepuller wire can also be less than half.

To constrain and secure the puller wire 28 on the blade 30 and as anadditional means to prevent adhesive failure and detachment, at least afirst inner heat shrink tubing 38 is placed on the blade 30, coveringand surrounding the spacers on both sides of the blade (with the pullerwire portions 28A, 28B trained through the spacers). In the illustratedembodiment of FIGS. 6A and 6B, the first inner heat shrink tubing 38 isfollowed by a second outer heat shrink tubing 40 that is placed over theassembly to surround and seal the components and the first heat shrinktubing 38. The first heat shrink tubing 38 may constructed of hightemperature resistant polyester (PET) or FEP. The second heat shrinktubing 40 may be constructed of extruded natural PEBAX or naturalPellethane. The uneven longitudinal edges E1 and E2 of the blade 30 helpgrasp and secure the first and second heat shrink tubings so they do notmigrate or slip during deflection.

In the illustrated embodiment of FIG. 1, the distal assembly 15comprises a generally straight proximal region and a generally circularmain region having at least one loop circling about 360 degrees, if nottwo loops circling about 720 degrees. The proximal region 98 is mountedon the deflectable section 14 and the main region 99 carries a pluralityof electrodes for mapping and/or ablation. With reference to FIG. 4, 5,the distal assembly 15 includes the shape memory support member 72, leadwires' 140 for the electrodes carried on the distal assembly 15, and acover extending the length of the distal assembly. The lead wires 140attached to the electrodes on the distal assembly 15 extend through anonconductive sheath 41 which extends from the distal assembly throughthe lumen half 19B of the deflectable section 14, through the cavityhalf 67B of the transition section 65, through the lumen 18 of thecatheter shaft 12, and into the control handle 16.

An electromagnetic position sensor (not shown) is mounted in or near thedistal assembly 15, e.g., in the distal end of the deflectable section14. A sensor cable 136 extends from the sensor into the half lumen 19Aof the deflectable section 14, the cavity half 67B of the transitionsection 65, the central lumen 18 of the catheter body 12 and into thecontrol handle 16 where it terminates in a suitable connector (notshown).

If irrigation at or near the distal assembly 15 is desired, anirrigation tubing 100 is provided to pass fluid from a source (notshown) along the catheter. In the illustrated embodiment, the irrigationtubing 100 extends through the control handle 16, the central lumen 18of the catheter body 12, and the half space 19B of the deflectablesection 14.

In use, a suitable guiding sheath is inserted into the patient with itsdistal end positioned at a desired location. An example of a suitableguiding sheath for use in connection with the present invention is thePreface™ Braiding Guiding Sheath, commercially available from BiosenseWebster, Inc. (Diamond Bar, Calif.). The distal end of the sheath isguided into one of the chamber, for example, the atria. A catheter inaccordance with an embodiment of the present invention is fed throughthe guiding sheath until its distal end extends out of the distal end ofthe guiding sheath. As the catheter is fed through the guiding sheath,the distal assembly 15 is straightened to fit through the sheath. Oncethe distal end of the catheter is positioned at the desired location,the guiding sheath is pulled proximally, allowing the deflectablesection 14 and distal assembly 15 to extend outside the sheath, and thedistal assembly 17 returns to its original shape due to itsshape-memory.

The user manipulating the actuator 13 on the control handle 16 actuatesdeflection mechanism inside the control handle to draw on a selectedpuller wire proximal portion 28A or 28B. Where distal portion 28A isselected, the deflection curvature DA on one side of the deflection beam30 initiates at or near the distal end of the compression coil A for adistinct curvature from the deflection curvature DB on the other side ofthe deflection beam 30. The force and stress on the puller wire 38 areminimized by the flat deflection beam and puller wire assembly whichtightly constrains the puller wire (with a round cross-section) to thebeam with a predetermined separation distance from the neutral bendingaxis of the deflection beam. The user may then rotate the generallycircular main region 99 of the distal assembly 15 by rotating thecontrol handle 16 which transfers torque to the catheter body 12 and thedeflectable section 14 through the transition section 65 therebetween bymeans of the half cylindrical members 66A and 66B to which the tubularstructures of the catheter body 12 and the deflectable section 14 arebonded by means of interlocking that melt into the perforations 68 inthe members 66A and 66B under heat fusion.

The preceding description has been presented with reference to presentlypreferred embodiments of the invention. Workers skilled in the art andtechnology to which this invention pertains will appreciate thatalterations and changes in the described structure may be practicedwithout meaningfully departing from the principal, spirit and scope ofthis invention. For example, the catheter can be adapted such that thethird puller wire advances and retracts another component such as aguide wire or a needle. As understood by one of ordinary skill in theart, the drawings are not necessarily to scale. Accordingly, theforegoing description should not be read as pertaining only to theprecise structures described and illustrated in the accompanyingdrawings, but rather should be read consistent with and as support tothe following claims which are to have their fullest and fair scope.

What is claimed is:
 1. A catheter, comprising: an elongated catheterbody comprising a first tubular structure having a first central lumen,a distal end and a proximal end; the first tubular structure having alayer of thermoplastic material, a deflectable section having a secondtubular structure having a second central lumen, and a proximal end thatis distal of the proximal end of the catheter body; the second tubularstructure having a layer of thermoplastic material; a joint between thedistal end of the first tubular structure and the proximal end of thesecond tubular structure, the joint including a first bracket with twofirst edges and a second bracket with two second edges, each brackethaving at least one receiving formation; a beam having a generallyrectangular cross-section with first and second opposing surfaces, atleast a portion of the beam extending through the joint; and a pullerwire having first and second main sections and a U-bend section betweenthe first and second main sections, the first and second main sectionsboth having an end anchored in a control handle at the proximal end ofthe catheter body, and the U-bend section being anchored to a distal endof the beam; wherein the two first edges are affixed to the firstsurface of the beam and the two second edges are affixed to the secondsurface of the beam such that the first and second brackets form ahollow body surrounding the portion of the beam, a distal portion of thehollow body being covered by the layer of thermoplastic material of thesecond tubular structure, a proximal portion of the hollow body beingcovered by the layer of thermoplastic material of the first tubularstructure, the layers of thermoplastic materials of the first and secondtubular structures each having at least one node extending into thereceiving formation.
 2. The catheter of claim 1, wherein an outersurface of each bracket is coated with an adhesive adapted to bond withthe layers of thermoplastic materials.
 3. The catheter of claim 1,wherein each receiving formation has a circular cross-section.
 4. Thecatheter of claim 1, where the receiving formations of each bracket arearranged in a predetermined offset pattern.
 5. The catheter of claim 1,wherein the first edges of the first bracket are affixed to outer edgesof the first surface of the beam, and the second edges of the secondbracket are affixed to outer edges of the second surface of the beam. 6.The catheter of claim 1, wherein each layer of thermoplastic material iscovered by a braided mesh.
 7. The catheter of claim 6, wherein eachlayer of braided mesh is covered by an elastomeric material.
 8. Thecatheter of claim 1, wherein the beam divides the hollow bodylongitudinally.
 9. The catheter of claim 1, wherein each bracket is madeof a high strength spring material.
 10. The catheter of claim 9, whereinthe high strength spring material is selected from the group consistingof stainless steel, nitinol and phosphor bronze.
 11. The catheter ofclaim 1, wherein the beam bisects the hollow body to form a first lumenhalf and a second lumen half, the first main puller wire sectionextending through the first lumen half and through the first centrallumen of the catheter body, and the second main puller wire sectionextending through the second lumen half and through the first centrallumen of the catheter body.
 12. The catheter of claim 1, furthercomprising a first compression coil having a proximal end at or near theproximal end of the catheter body and a distal end distal of the joint,the first compression coil having a coil lumen through which a portionof the first main puller wire section extends.
 13. The catheter of claim12, wherein the first compression coil extends through the first centrallumen of the catheter body and through the first lumen half.
 14. Thecatheter of claim 12, further comprising a stop having a bore configuredto receive a distal end of the first compression coil with the firstmain puller wire section therein extending through the bore, the stopconfigured to affix the first compression coil to the first surface ofthe beam.
 15. The catheter of claim 1, further comprising at least onespacer extending axially on at least one surface of the beam configuredto provide a predetermined separation distance between the respectivepuller wire section and the at least one surface of the beam.
 16. Thecatheter of claim 15, further comprising at least one heat shrink tubeconstraining the spacer and its puller wire section to the beam.
 17. Thecatheter of claim 15, wherein the at least one spacer includes anextrusion.
 18. The catheter of claim 15, wherein the at least one spacercomprises an adhesive layer and a tubing.
 19. The catheter of claim 12,further comprising a heat shrink tube surrounding the first compressioncoil.